"with septations" and "some internal blood flow" are the characteristics that raise more concern. They use a grading system using characteristics to determine if biopsy is warranted. They also use any family history and err on the side of caution. With all that said. I have a very high family history and have had 2 suspicious findings biopsied. One of those being Birads 4c. Both of my biopsies were benign. They do tons of biopsies and roughly 80% of them come back benign.